Patent Application
20070041504
The present invention relates generally to an x-ray target assembly and more particularly to an x-ray target assembly with separate hub and disc elements.
Modern medical imaging assemblies have increased in complexity and capabilities. These increases often result in an increase in power requirements and associated wear on such assemblies. Such is the case with x-ray tube assemblies. Increases in power requirements of the imaging assembly can result in increases in the required rotational speed of the x-ray target assembly in order to prevent overheating and damage thereto. These increased rotational speeds may result in high hub stresses that exceed present design criteria. The hub is the center portion of a target assembly in communication with the drive shaft.
In addition to the additional stresses associated with the increase in power requirements, the target assembly itself will suffer an increase in wear and thermal damage. These increases stressors are well known to result in damage to the impact regions of the target element. In addition, the thermal energy may translate through the target assembly to enter the hub portion. The increase in thermal energy in combination with the increased stresses due to increased rotational speeds may result in undesirable wear and damage to the hub element.
In any design for an x-ray target assembly it is likely that the target element or portions thereof will suffer damaged during prolonged usage. This is simply a preordained result of the target element being impacted by an electron beam to facilitate the generating of x-rays. Yet when wear or damage becomes too great, existing designs require complete replacement. Disassembly and repair is not contemplated by existing designs and may be impractical based on design configurations and associated costs. Since such wear and damage may only be minimized, a design that introduced the potential for worn or damaged portions of the target element to be replaced would be beneficial. In addition, where repair is still not cost effective, a design that allowed reuse of at least a portion of the target assembly would provide desirable cost benefits.
It would, therefore, be highly desirable to have an x-ray tube target assembly that allows for simplified replacement of worn or damaged portions of the target element. It would also be highly beneficial to have an x-ray tube target assembly that was capable of withstanding the high rotational speeds and increased thermal requirements of modern anode performance.
An x-ray target assembly is provided comprising a center hub element affixed to a drive shaft and an outer disc including a plurality of tab extensions removably engaging the periphery of the center hub element. A target element is mounted on an upper outer disc surface.
Other features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.
Referring now to
The impact of electrons on the x-ray tube target assembly 24 generates considerable heat and considerable wear. The present invention contemplates such stressors by forming the x-ray tube target assembly 24 as a center hub element 26 and an outer disc 28. A target element 30 is mounted to the outer disc 28. The outer disc 28 is removably mounted to the center hub element 26 such that if the target element 30 experiences undesirable levels of wear or damage, the outer disc 28 may be replaced while the hub element 26 remains. In addition to replacement, the present design allows to cost savings through reuse of non-damaged portions of the target assembly 24 in new assemblies. Molybdenum, used in target assemblies 24, is expensive and the present invention allows its reuse to provide beneficial cost savings. In addition, the hub element 26 may be optimized to withstand the stresses transmitted to it by the anode drive assembly 20, while the outer disc 28 may be optimized to withstand the thermal energy associated with electron bombardment.
In one particular embodiment, the hub element 26 has a hub cross-sectional width 32 that is increased to reduced stresses due to centrifical loading transferred from the anode drive shaft 22. In addition, the outer disc 28 is preferably comprised of an outer disc cross-sectional width 34 located at the outer perimeter 35 of the outer disc 28 and an inner disc cross-sectional width 36 located at the inner perimeter 38 of the outer disc 28. The inner disc cross-sectional width 36 is preferably smaller than the outer disc cross-sectional width 34 to prevent thermal transfer from the target element 36 to the hub element 26. A taper 40 may be formed in the transition between the inner disc cross-sectional width 36 and the hub cross-sectional width 32 to further reduce stresses. The target element 36 is preferably mounted to an upper outer disc surface 42 of the outer disc 28.
It is contemplated that the target assembly 24 may be formed in a variety of configurations such that the outer disc 28 is removably mounted to the center hub element 26. One such embodiment, illustrated in
While it is contemplated that the outer disc 28 may be formed as a single element, the advantages of inexpensive assembly, salvage, or repair provided by the present invention are further increased if the outer disc 28 is comprised of a plurality of partial circumferential disc portions 54. A tab extension 44 may be formed on the inner partial disc perimeter 56 of each partial circumferential disc portion 54. By forming the outer disc 28 from a plurality of partial disc portions, if a small segment of the target element 36 is damaged, only the partial circumferential disc portion 54 in question need by replaced or removed prior to salvage. This provides an unheralded level of reuse, maintenance, and cost effectiveness to x-ray tube targets.
Although the partial circumferential disc portions 54 may by assembled in a variety of fashions, one embodiment contemplates the use of side tabs 58 formed on a first radial side 60 of the partial circumferential disc portion 54. Opposing the side tab 58 on a second radial side 62 is formed a side slot 64. In this fashion, as seen in
While particular embodiments of the invention have been shown and described, numerous variations and alternative embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.
